Formation testers, such as packer-based formation testers, have a large volume of fluid trapped between the packers. This trapped fluid is a mixture of one or more of drilling mud, filter cake (solid portion of the drilling mud), and drill formation bits suspended in the mud during drilling as cuttings or dislodged during the running of the tool. The fluid is also characterized as a slurry or suspension.
During testing, the trapped fluid contaminates the fluids entering the closed area between the packers, and it is time-consuming to pump the fluid. Furthermore, the fluid is prone to plugging screens in the pump and causing premature valve failure in the pumping system.